In vivo 5-fluorouracil-[corrected]induced apoptosis on murine thymocytes: involvement of FAS, Bax and Caspase3.

Apoptosis is a highly regulated and programmed cell breakdown process characterized by numerous changes. It was reported as the major mechanism of anticancer drug-induced cells death. Unfortunately, many of these drugs are non-specific and cause severe side effects. The effects of 5-fluorouracil (5-FU) on the apoptotic events in normal murine thymus were evaluated using an in vivo model. A single dose of 5-FU (150 mg/kg ip) was injected to CF-1 mice. A multiparametric analysis of thymic weight, cellularity, viability, architectural organization, apoptosis, DNA fragmentation, and the expression of several apoptotic proteins was evaluated in 10 days time-course study post-5-FU dosing. Total organ weights, thymocyte counts, and cell viabilities diminished drastically from the second day. The thymus architecture assessed through electron scanning microscopy revealed deep alterations and the lost of cell-cell contact between the first and the third days. DNA fragmentation and apoptotic indexes (May Grünwald Giemsa staining, double fluorescent dyes, and TdT-mediated dUTP nick-end labeling assay) revealed that cell death was maximal on the second day (three times over control). Furthermore, the pro-apoptotic proteins FAS and Bax were strongly up-regulated during the first 2 days. The aforementioned morphological and biochemical changes were also accompanied within the same period by caspase 3 activation. This study revealed that in vivo apoptosis in normal thymus after 5-FU administration is related to FAS, Bax, and Caspase 3 co-expressions under the current experimental conditions, these findings, therefore, contribute to a new insight into the molecular mechanisms involved during 5-FU administration upon the thymus and the possible events committed in the lymphophenia associated with chemotherapy.

Comparative studies of erythroid growth factors

Se evaluó la aparición de factores séricos capaces de estimular la proliferación de progenitores eritroides mamíferos. Sueron anémicos y normales de ambos e jemplares, fraccionados por tratamiento alcohólico, se ensayaron por el método del ratón post-hipóxico, no detectándose incorporación de 59Fe. Al ser ensayados en cultivos semisólidos de médula ósea murina a diferentes tiempos de incubación (colonias CFU-E y BFU-E), el suero anémico aviario mostró alta actividad estimulatória, mientras que el suero anémico anfibio resultó incapaz de incrementar la proliferación eritroide. La muestra aviaria parcialmente purificada por tratamiento alcohólico fue cromatografiada en Sephadex G-150 revelando tres entidades moleculares respondables de la actividad biológica in vitro, con pesos moleculares aparentes de 29, 14 y 10 KD respectivamente. Los factores séricos aviarios estimulantes de la línea eritroide fueron sometidos a diversos tratamientos físico-químicos y luego se evaluó la conservación de su actividad biológica. Todos ellos resultaron termoestables, sensibles al tratamiento con neuraminideasa, mientras que el ditiotreitol provocó la pérdida de la actividad biológica de las proteínas de bajo peso molecular. Estos resultados sugieren, al menos bajo estas condiciones experimentales, la presencia de factores análogos estimulantes del crecimiento eritroideo entre amniotas homeotermos